1. Field of the Invention
The present invention relates to a shake detector used for a shake correction mechanism of an imaging apparatus.
Priority is claimed on Japanese Patent Application No. 2007-315732, filed Dec. 6, 2007, the content of which is incorporated herein by reference.
2. Description of Related Art
Conventionally, in an imaging apparatus, such as a camera, there have been proposed various kinds of hand shake correction mechanisms that suppress image blur on an imaged surface of an imaging element, which is caused by hand shake or the like, by shifting an optical system or the imaging element in a planar direction perpendicular to an optical axis according to the amount of shake occurring at the time of photographing. Moreover, in such a hand shake correction mechanism, a shake detector is used to determine the shift position of the optical system or the imaging element. As such a shake detector, there are various shake detectors. For example, Japanese Unexamined Patent Application, First Publication No. 2006-313385 discloses a technique of making it possible to adjust a zero point of shake detection, that is, the amount of shake detection when the shake amount of an imaging apparatus is zero to zero.
FIG. 4 shows the relationship between the amount of shake occurring at the time of photographing with an imaging apparatus and the shift amount by which an optical system or an imaging element is made to move in a planar direction perpendicular to the optical axis. A solid line 400 of FIG. 4 indicates those described below. That is, when the amount of shake in the + direction occurs at the time of photographing with an imaging apparatus, the shake is corrected by setting the shift amount of an optical system or an imaging element in the + direction according to the amount of shake. In addition, when the amount of shake in the − direction occurs at the time of photographing with the imaging apparatus, the shake is corrected by setting the shift amount of the optical system or the imaging element in the − direction according to the amount of shake. In addition, when the amount of shake occurring at the time of photographing with the imaging apparatus is zero, the shake is not corrected by setting the shift amount of the optical system or the imaging element to zero.
That is, when there is no error of a zero point like the solid line 400 of FIG. 4, the optical system or the imaging element can be suitably shifted in the planar direction perpendicular to the optical axis according to the amount of shake occurring at the time of photographing with the imaging apparatus. However, when there is an error of a zero point like a dotted line 410 of FIG. 4, the optical system or the imaging element cannot be suitably shifted in the planar direction perpendicular to the optical axis according to the amount of shake occurring at the time of photographing with the imaging apparatus. As a result, the quality of a photographed image is degraded. That is, in order to detect the amount of shake occurring at the time of photographing with high precision, it becomes necessary to correct a zero point with high precision at the time of photographing.
FIG. 5 shows an example of the relationship between an amount of shake detection and a time when there is no shake occurring at the time of photographing with an imaging apparatus. As indicated by the solid line 500 of FIG. 5, the amount of shake detection when there is no shake of the imaging apparatus changes due to changing external factors, such as an offset voltage and an ambient temperature, even though there is no shake occurring in the imaging apparatus. For this reason, the shake detector detects a change in the amount of shake detection and performs correction such that the amount of shake detection always matches the zero point. Since this change does not include the amount of shake occurring in the imaging apparatus and the change is also very gentle, the zero point can be corrected with high precision.
FIG. 6 shows an example of the relationship between an amount of shake detection and a time when there is shake occurring at the time of photographing with an imaging apparatus. As indicated by a solid line 600 of FIG. 6, the amount of shake detection when there is shake of the imaging apparatus largely changes due to not only changing external factors, such as the offset voltage and the ambient temperature, but also shake occurring in the imaging apparatus. For this reason, the shake detector detects a change in the amount of shake detection and performs correction such that the amount of shake detection always matches the zero point. In order to calculate the amount of shake detection when shake does not occur while shake is occurring in the imaging apparatus, it is necessary to perform signal processing for removing shake, for example, to average shake detection signals including the amount of shake.